The ETSI Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN) works on creating requirements, network architecture and related protocols of the Next Generation Networks (NGN). Logically the NGN includes three layers: data bearing layer, bearer control layer, and service control layer. Generally there are two systems in the bearer control layer: Network Attachment Subsystem (NASS) and Resource and Admission Control Subsystem (RACS). The NASS carries out address and authentication management for users, and provides user location information for the service control layer and the RACS. The RACS manages bearer network resources, and performs admission control for Quality of Service (QoS) requests of the service control layer. A brief introduction of this is as follows.
The structure of a TISPAN RACS is illustrated in FIG. 1. The Session Policy Decision Function (SPDF) is a service-based policy decision function module, providing a Gq' interface for the service control layer and providing a bearer service for an application function (AF). The interface receives service-based QoS requests from the service control layer. When a user requests a service, a session is established with the AF. The AF extracts required QoS parameters according to the service request in the session, and requests the SPDF for bearer service. The request includes type of service, bandwidth, quintuple information of flow, user representation, flow operation instruction and so forth. That is, the service control layer requests the bearer control layer to set a QoS channel for a particular service. Policy rules are stored at the SPDF to make service-based decisions. The SPDF locates an access gateway, related resources and a control entity A-RACF of the user, and transfers the QoS request to the A-RACF via Rq interface. The A-RACF carries out admission control of QoS. The A-RACF receives the QoS request for an access network managed by the A-RACF via the Rq interface, acquires user profile data and location information (which are provided by the NASS, detailed description will not be given herein.) via an e4 interface, and determines whether the network can provide QoS for the user. A clear response of admission/non-admission is given to the SPDF by bandwidth reservation or after implementing QoS to a bearer layer entity.
If the QoS request can be implemented, the A-RACF sends a command to a RCEF and an Access Node (ΔN) through RE and RA interface operations, according to flow status as indicated in the request. Located in an edge device of the access network, the RCEF carries out QoS implementation.
In addition, the SPDF instructs a C-BGF to implement QoS via Ia interface, which also performs NAT.
The functionality architecture of the RACS can support management, control and implementation of user end-to-end QoS, provide reference function decomposition and interfaces for operators such as network operators and service providers, and provide authentication and accounting capabilities between different providers. The NASS stores user profile information and performs access authentication and accounting, address allocation, user network parameter configuration, user end device management, etc. The RACS carries out QoS control and management. With the RACS, the bearer control layer can control each network element of the service control layer, which makes the network manageable and operable. Also, the bearer control layer provides a uniform access interface, covering the differences of different networks. The service control layer performs service-related control and provides management of a variety of services for users.
FIG. 2 illustrates the structure of an NASS. As illustrated in FIG. 2, the NASS includes (1) an Access Management Function (AMF) entity, adapted to coordinate and forward network access requests initiated by a user terminal device, request a Network Access Configuration Function (NACF) entity to assign an IP address and other network parameters to the user terminal device, and interact with a User Access Authorization Function (UAAF) entity for user authentication, authorization, access denial and so forth; (2) an NACF entity, adapted to assign an IP address to a user terminal device, and distribute other network parameters to the user terminal device, such as a Domain Name Server (DNS) address and a session signaling proxy address; (3) a Connectivity Session Location Function (CLF) entity, adapted to associate the identity of a user with physical/geographical location information, IP address and other location information when a user uses a particular connectivity session service, provide a query interface between the service control layer an the bearer control layer, and provide related information of the user bear network required by the service control layer for the service control layer, such as a user ID and user location information; (4) a User Access Authorization Function (UAAF) entity, adapted to perform authentication and authorization of a user accessing the network, and send activation and profile information of the user to the CLF via a4 interface; and (5) a Profile Data Base Function (PDBF) entity, adapted to store subscriber authentication information, user identity authentication methods, additional important data, etc.
The NASS also includes the following system interfaces (1) an e1 interface, between an AMF and a user terminal device, through which a user terminal device initiates an access request to a network, in which an Access Relay Function (ARF) entity can implement relay function of the access request and insert location information of the network that the user terminal device accesses; (2) an e2 interface, between a CLF and a service control and application subsystem, through which the NASS provides for the service control and application subsystem user access location information (e.g., an access device identifier, a route identifier), access authentication result, etc; and (3) an e4 interface, between a CLF and a RACS, through which the NASS provides user access location and QoS subscription information for the RACS, and by which the RACS determines resource allocation and whether resource allocation meets a service requirement according to an access device and an accessing method of the user.
Seen as part of a network model, the SPDF belongs to a Network Service Provider (NSP) which provides Internet access services, normally providing a core network, and provides IP addresses for users. The A-RACF belongs to a Network Access Provider (NAP) operating a network access device with which a user can access the core network. Normally the A-RACF is embodied as an access resource management and admission control server managing access network resources and performing admission control of QoS requests. Different NAPs handle network accesses in different areas. When multiple NAPs of different areas access the core network of one NSP, functionally, there is one SPDF connected with multiple A-RACFs. Furthermore, as illustrated in FIG. 3, the AMF belongs to an NAP, and the NACF, the CLF and the UAAF belong to an NSP.
In FIG. 3, two NAP1 and NAP2 are connected to an NSP (user management server). User management is carried out at the NSP. Each NAP includes an AMF and an A-RACF.
This issue is briefly discussed in the draft standards of RACS at present. An SPDF finds an A-RACF based on local configuration. Practically, information that can be used by the SPDF is merely user identifier and IP address information from an AF. Home domain information can be carried in the user identifier. However, if a user visits another network, a correct A-RACF cannot be found based on the home domain information. As illustrated in FIG. 3 about user IP address space, because IP addresses are assigned collectively at an NSP, if different IP address spaces are assigned to different NSPs, corresponding A-RACFs can be found based on a corresponding relationship between the IP address spaces and A-RACF addresses configured at the SPDF. However this limits the network. For example, a correct A-RACF can not be found when a user changes his access location carrying his IP address with him. In practice, multiple access resource management and admission control servers may be cascaded, which results in the problem in the existing systems for an upper-level access resource management and admission control server to find a lower-level access resource management and admission control function server.